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#ptp
2 posts
Precision timing
8 min
The clock that rang like a bell under load
I built a PRU clock that held nanoseconds on the bench, then rang under load. The daemon crossing its ticks into CLOCK_REALTIME was modeling chrony's own steering and feeding the model back. I fixed it by moving the reference out of userspace, into a Linux PTP hardware clock.
#gps#pps#ptp#beaglebone
Precision timing
8 min
The frozen clock that nobody noticed
A GPS-disciplined NTP server stopped being disciplined, and every monitor stayed green. The giveaway was a freq_ppb value that repeated byte-for-byte across three seconds, which a live servo never does.
#ptp#ntp#gps#linux